Pressure release valves are well known, and are commonly used in fuel systems for opening at a preset pressure difference across the valve until the pressure difference is reduced to a preset level. For example, such valves allow fuel vapor to be vented from a fuel tank when the pressure in the fuel tank increases unacceptably above ambient.
Conventionally, such valves include a valve element configured for reversibly sealing against a valve seat, a sensing element such as a diaphragm or piston across which the pressure difference is to be regulated, and a reference force element, for example a spring, that sets the pressure difference at which the valve is to open.